This invention relates generally to gas turbines and more particularly to fuel control systems for gas turbines.
Referring to FIG. 2, at least one known prior art industrial gas turbine gas fuel control system 200 relies upon steady fuel pressure P2 upstream of a set of parallel gas control valves 202, 204. For this reason, a pressure control valve 206 is employed immediately upstream of parallel gas control valves 202, 204 to regulate this intervalve pressure P2.
Persistent oscillation of fuel intervalve pressure P2 resulting from gas fuel supply pressure P1 variations can become a problem in gas turbine fuel control systems 200. Prior art proportional 208 plus integral 210 controls react solely to P2 error, and consequently has poor P1 disturbance rejection capability. Thus, gas supply pressure P1 variation can cause gas fuel intervalve pressure P2 to oscillate as a result of the lack of disturbance rejection in prior art gas turbine fuel control systems.